Just back from a trip to Maine. 5 hours across on secondary roads, mostly under 60 and a lot under 50. A/C on the whole time. Really a great trip for a 30yo car as the likeihood of getting trapped in standing traffic is nil, and anyway, who wants to sit in a Honda Fit for 5 hours one way?

We were three grownups, with luggage (so heavily freighted) and with a rear mounted bike rack hanging off the trunk. My mileage appeared to be around 27mpg. I have never gotten mileage so low-- its usually around 34-35.

Just how much drag is a bike rack anyway? Should I charge my wife extra?

I don't know how well it translates but I have heard that every 100-150 lbs added tends to take 1mpg off, so with 4 adults and their luggage I'd hardly be surprised at that mileage. With my roof rack I lose about 2mpg on the highway.

Doubtful on the fuel leak since no odor of fuel and I have both belly pans installed.

But lots of hills, lots of downshifting.

Im usually careful about not resetting the trip od but some kind of record keeping malfunction may be to blame. I also had to refill with a truck nozzle and the display on the pump was unreadable. I had to accept the credit card receipt as gospel.

FYI When driving from KY to FL in my 87 300SDL I get 30 mpg with no bike rack and 22 mpg with rack with three bikes - all other things being equal. This is 70 mph on (almost) all interstate. I assume wind resistance. It's surprising. This car gets 25 overall.

Top Gear did a show on wind resistance. I wish I could recall the two cities they cited but the overall premise was that you would save money by having a bicycle shipped by rail rather than by using a bike rack.

Mercedes designed a very aerodynamic car after the Box Fish.

It has a very low drag coefficient, I want one.

The extra weight will also reduce your MPGs and might have made you nose high, tail low increasing wind resistance.

Sounds like the trip was fun and should be done again without the bicycle rack. Report your results back

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1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 April 2018.

I would put it mostly to the bike rack. Weight is not much of a factor on the highway and could even increase it by lowering the car.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual. It still needs upholstery redone...I also have a 427 Cobra replica with an aluminum chassis.

FYI When driving from KY to FL in my 87 300SDL I get 30 mpg with no bike rack and 22 mpg with rack with three bikes - all other things being equal. This is 70 mph on (almost) all interstate. I assume wind resistance. It's surprising. This car gets 25 overall.

Since I have full body pans I dont think wind resistance is much altered. But trust me-- with 76 hp at your full command, you can tell when there is one extra person in the car, let alone two!

I was treated well in Me: At one point we parked along the road to hike into the woods and when we returned there was a message on the car from someone:
"If you are broken down, call me-- I am a Benz owner too! If not, nice car!"

I called and turned him onto peachparts. He had a 59 ponton, a 300sdl, and a 240d.

I've never found hills to affect mileage much. you pull them and then coast down the other side.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual. It still needs upholstery redone...I also have a 427 Cobra replica with an aluminum chassis.